      (all-closed-sets G clop #{}))
   ([G clop initial]
      (let [G (if (set? G)
-	       (improve-basic-order G clop)
-	       G)]
+               (improve-basic-order G clop)
+               G)]
        (binding [subelts (memoize subelts)]
-	 (take-while identity
-		     (iterate (partial next-closed-set G clop)
-			      (clop initial)))))))
+         (take-while identity
+                     (iterate (partial next-closed-set G clop)
+                              (clop initial)))))))
 
 (defn all-closed-sets-in-family
   "Computes all closed sets of a given closure operator on a given set

  "Implements oplus from the Next Closure Algorithm."
  [G clop A i]
  (clop (set (conj (filter #(contains? A %) (subelts G i))
		   i))))

(defn next-closed-set-in-family
  "Computes next closed set as with next-closed-set, which is in the

  on base-set."
  [base-set pairs]
  (transitive-closure (union (set pairs)
                             (set-of [x x] [x base-set]))))

(defn graph-of-function?
  "Returns true iff relation is the graph of a function from source to target."
